1. Field of the Invention
The present invention relates to a phosphor device, and an illumination apparatus and projector apparatus, both using the phosphor device.
2. Description of the Related Art
Some light source apparatuses use a phosphor that emits a light beam having a wavelength different from that of the excitation light coming from a light source and applied to the phosphor. The light source apparatus of this type is utilized as a light source in, for example, illumination apparatuses and image display apparatuses.
The light source apparatus of this type has a light source, which is a semiconductor light source, such as a light emitting diode (LED) or a laser diode (LD), in most cases. In the light source, phosphor particles are dispersed in a resinous binder, such as transparent silicone or epoxy resin, forming a light emitting layer.
The resinous binder may be degraded with the excitation light coming from the semiconductor source, or may be damaged if the excitation light has high intensity. The resin, such as silicone or epoxy resin, in which the phosphor is dispersed, has low thermal conductivity. The temperature of the phosphor therefore rises, inevitably shifting the emission wavelength of the phosphor or causing a phenomenon such as temperature quenching that lowers the emission intensity. Consequently, the luminance the light source apparatus achieves will decrease.
A technique which involves use of an inorganic transparent material such as transparent silicone or epoxy resin as a binder in place of a resinous binder is known. Jpn. Pat. Appln. KOKAI Publication No. 2003-258308 discloses the use of a transparent inorganic material such as glass. Jpn. Pat. Appln. KOKAI Publication No. 2006-282447 and Jpn. Pat. Appln. KOKAI Publication No. 2010-024278 discloses the use of a ceramic having high thermal conductivity.
The light emitting layer composed of the transparent ceramic binder and phosphor is used in place of the above-mentioned phosphor layer composed of the resinous binder and phosphor in most cases. Inevitably, the transparent ceramic binder does not have a structure fit for use in a light source apparatus configured to emit light from phosphor.